console: do not load config in module to save it in backendscfg

Currently we load the given config in the module's config objet, and then save it. There are two problems:

1. it supplies params 'as it', so external commands are not interpreted
2. even if we called the external command before, it may save the loaded value instead of the command line

Also, there is no reason to validate the config with the module, as all constraints were validated during call of ask().

Fixes #392 (closed) and #374 (closed)